1. Field of the Invention
The present invention relates to an improved polyolefin resin composition and more particularly, to a polyolefin resin composition comprising a polyolefin, e.g. polypropylene, an inorganic filler, and a hydrogenated styrene-butadiene rubber which possesses improved mechanical properties such as excellent scratch resistance, good surface strength, good heat resistance, and good impact strength. Advantageously, the composition can be used as a material for the crash pad of a vehicle.
2. Description of the Related Art
Various types of materials used as a crash pad for vehicles are well known in the art. Generally a crash pad for a vehicle comprises three basic types. A first type is composed of a basic substance, foam and a covering; a second type is composed of a basic substance and a part pad (foam plus covering), and a third type is composed of only the basic substance. In fact, various types of vehicles except luxurious vehicles use crash pads which constitute only the basic substance of the above three types. At the present time, the basic substance mainly includes acrylonitrile-butadiene-styrene copolymer and polycarbonate or polypropylene. Polypropylene material has been used because of its inexpensive cost. Accordingly, the use of propylene material is being investigated as an improvement in the art.
Recently, in order to follow the moving trend of using lightweight materials and cost reduction, improvements in plastic elements are actively being sought. One of the typical examples of such a resinous composition is one containing polypropylene. Such a resinous composition which contains an inorganic filler has the advantages of excellent heat resistance, good mechanical strength, and dimensional stability. However, it also possess disadvantages of low impact resistance and reduced scratch resistance so that such prior olefin resin compositions are not resistant to crease-whitening (inner scratch irrodition).
The above type olefin resin compositions are disclosed in Japanese Laid-Open Patent No. 54-43250 which relates to a composition comprising 0.1-100 wt % of an inorganic filler and a polyolefin; Japanese Laid-Open Patent No. 56-88447 which relates to an ethylene/propylene copolymer consisting of 90-98.5% by weight of polycrystalline propylene, 5-0.5 wt % noncrystalline ethylene/propylene copolymer containing 20-90 mol % ethylene unit, and 5-1 wt % crystalline ethylene homopolymer, and Japanese Laid-Open Patent No. 7-145278 which relates to a propylene polymer resin composition produced by incorporating 100 pts. by wt. of polypropylene with 1-10 pts. by wt. of hydrogenated SBR (styrene-butadiene rubber).